Method and apparatus for generating radiation utilizing DC to AC conversion with a conductive front

Abstract

Method and apparatus for generating radiation of high power, variable duration and broad tunability over several orders of magnitude from a laser-ionized gas-filled capacitor array. The method and apparatus convert a DC electric field pattern into a coherent electromagnetic wave train when a relativistic ionization front passes between the capacitor plates. The frequency and duration of the radiation is controlled by the gas pressure and capacitor spacing.

What is claimed is: 
     
       1. Method for generating radiation, comprising the steps of: producing a static DC electric field configuration; and   propagating a conductive front of plasma through said electric field to cause selective discharge of current through said field, said selective discharge of current generating electromagnetic radiation behind said front which is emitted from said field.   
     
     
       2. Method as set forth in claim 1, further comprising the step of selecting the wavelength of said emitted electromagnetic radiation by selectively varying dispersive properties of a medium behind the conductive front of said DC electric field configuration. 
     
     
       3. Method as set forth in claim 2, wherein said step of selecting the wavelength of said emitted electromagnetic radiation comprises selecting said wavelength to be within the range of about 1 cm-1 μm. 
     
     
       4. Method as set forth in claim 1, further comprising the step by selecting the peak power of said emitted electromagnetic radiation by selectively varying the amplitude of said DC electric field configuration. 
     
     
       5. Method as set forth in claim 4, wherein said static DC electric field configuration is produced by a bias voltage, and said step of producing said static DC electric field configuration comprises pulsing said bias voltage to increase said peak power of said emitted electromagnetic radiation. 
     
     
       6. Method as set forth in claim 1, where in said step of propagating a conductive front comprises propagating an ionization front in an ionized plasma. 
     
     
       7. Method as set forth in claim 1, wherein said step of producing said static DC electric field configuration comprises producing said static DC electric field configuration within a gas-filled capacitor array, and said step of propagating a conductive front comprises propagating a pulse of visible radiation through said array which ionizes said gas and produces a phased discharge current across said array, resulting in the emission of said electromagnetic radiation from said array. 
     
     
       8. Method as set forth in claim 7, wherein said step of propagating visible radiation comprises propagating laser radiation. 
     
     
       9. Method as set forth in claim 8, wherein said step of producing a static DC electric field configuration comprises filling said capacitor array with pressurized gas. 
     
     
       10. Method as set forth in claim 9, further comprising the step of selecting the wavelength of said emitted electromagnetic radiation by selectively varying dispersive properties of said gas behind said conductive front. 
     
     
       11. Method as set forth in claim 9, further comprising the step of selecting the wavelength of said emitted electromagnetic radiation by selectively varying said pressure of said gas. 
     
     
       12. Method as set forth in claim 11, wherein said step of varying said pressure of said gas comprises varying said pressure within the range of about 0.1 milliTorr-10 Torr. 
     
     
       13. Method as set forth in claim 7, wherein said step of producing said static DC electric field configuration within said capacitor array comprises producing said static DC electric field configuration with multiple, spaced-apart capacitors, and further comprising the step of selecting the wavelength of said emitted electromagnetic radiation by selectively varying the spacing between said capacitors. 
     
     
       14. Method as set forth in claim 1, wherein said step of producing said static DC electric field configuration comprises varying an amplitude of a DC electric field throughout said DC electric field configuration field. 
     
     
       15. Method as set forth in claim 14, wherein said step of varying an amplitude comprises varying said amplitude in undulating fashion. 
     
     
       16. Method as set forth in claim 14, further comprising the step of altering the amplitude of said variations in selected regions of said DC electric field for generating said emitted radiation with a selected amplitude versus time signature. 
     
     
       17. Method as set forth in claim 14, further comprising the step of altering the spatial frequency of said amplitude variations in selected regions of said DC electric field for generating said emitted radiation with a selected frequency versus time signature. 
     
     
       18. Method as set forth in claim 14, further comprising the step of reducing said amplitude variations to zero in selected regions of said DC electric field for generating said emitted radiation encoded with missing wave periods. 
     
     
       19. Method as set forth in claim 1, further comprising the step of selecting the duration of said emitted electromagnetic radiation by selectively varying the amount of time that said conductive front propagates through said electric field. 
     
     
       20. Method as set forth in claim 1, further comprising the step of selecting the waveform of said emitted electromagnetic radiation by selectively varying the waveform of said DC electric field configuration. 
     
     
       21. Method as set forth in claim 1, wherein said step of producing said DC electric field configuration comprises producing an electric potential within the range of about 1-30 kV. 
     
     
       22. Method as set forth in claim 1, further comprising the step of selecting a pulse length of said emitted electromagnetic radiation by selectively varying the number of cycles of said DC electric field configuration. 
     
     
       23. Method as set forth in claim 22, wherein said step of producing said DC electric field configuration comprises producing said DC electric field configuration by an array of charged capacitors, and varying said pulse length of said emitted electromagnetic radiation by selectively removing the charge from one or more of said capacitors in the array. 
     
     
       24. Apparatus for generating radiation, comprising: means for producing a static DC electric field configuration; and   means for propagating a conductive front of plasma through said electric field to cause selective discharge of current through said field, said selective discharge of current generating electromagnetic radiation behind said front which is emitted from said field.   
     
     
       25. Apparatus for generating radiation, comprising: a gas-filled capacitor array;   a DC bias voltage applied to said array to produce a static DC electric field within said array; and   a laser source for propagating laser radiation pulses through said electric field to ionize said gas within said array and produce a phased discharge current across said array, said current generating electromagnetic radiation which is emitted from said array.   
     
     
       26. Apparatus as set forth in claim 25, wherein said capacitor array comprises a plurality of adjacent capacitors, each of said capacitors including a respective pair of spaced-apart, opposed capacitor plates with pressurized gas disposed therebetween. 
     
     
       27. Apparatus as set forth in claim 26, wherein said pressurized gas is selected from the group consisting of azulene, diethyl aniline, hydrogen, helium and carbon monoxide. 
     
     
       28. Apparatus as set forth in claim 26, wherein said capacitors in said capacitor array have centers which are respectively separated from each other by a distance of about 4.7 cm to 300μ. 
     
     
       29. Apparatus as set forth in claim 28, wherein said capacitor array comprises 1-100 capacitors. 
     
     
       30. Apparatus as set forth in claim 26, wherein adjacent capacitors in said array are oppositely polarized. 
     
     
       31. Apparatus as set forth in claim 25, wherein said laser source is selected from the group consisting of Nd:Glass, Nd:Yag, and Ti:Sapphire lasers. 
     
     
       32. Apparatus as set forth in claim 25, wherein said laser source produces radiation with a wavelength in the range of about 0.25μ-1.0μ. 
     
     
       33. Apparatus as set forth in claim 32, wherein said laser source produces radiation with a pulse length in the range of about 0.2 mm to 15 mm. 
     
     
       34. Apparatus as set forth in claim 25, wherein said DC bias voltage is in the range of about 1-30 kV.